Cancer is the leading cause of death over the world, and it accounts for a high percentage. The survival rate of cancer patients has been increased as a result of progression of cancer diagnosis methods and cancer treatment methods. However, it is still difficult for people living in developing countries, which account for 75% of the entire global population, to receive advanced cancer therapy. As such, it has been desired to develop an inexpensive cancer therapy.
In contrast with advanced medical treatments, natural treatments of using herbs and the like have been known from old times. Ayurveda is one type of natural treatment that has practiced in India from B. C. Roots of the medical herb ashwagandha (scientific name: Withania somnifera; which is also referred to an Indian carrot, Indian ginseng or Winter cherry), which are used in the Ayurveda, have been known to have a nourishment-enhancing action, a health-promoting action and the like.
The present inventors had previously found that an alcohol extract of ashwagandha leaves exhibits an anticancer activity (Patent Literature 1). Such an alcohol extract of ashwagandha leaves comprises, as active ingredients, withanolides such as withanone and withaferin A represented by the following formulae:
Thus, the alcohol extract of ashwagandha leaves kills cancer cells based on mechanisms such as apoptosis or growth inhibition. In an in vitro test, withanone exhibits selective cytotoxicity to cancer cells, whereas withaferin A has effects even on normal cells. By adding withanone and withaferin A to a cell culture solution, normal cells can be protected from the cytotoxicity of withaferin A by the action of withanone.
Also, the present inventors had previously found that a water extract of ashwagandha leaves has an anticancer activity (Patent Literature 2). In such a water extract of ashwagandha leaves, the contents of withanone and withaferin A are low, and triethylene glycol has been known to be a main anticancer component (Non Patent Literature 1).